Performing the Galileo mission using the S-band low-gain antenna

Following the failure of Galileo´s X-band high-gain antenna to deploy in April 1991, an alternate approach which utilizes the spacecraft´s S-band low-gain antenna has been conceived and is in development. This approach will enable the accomplishment of at least 70 percent of Galileo´s original scientific objectives. Implementation is to be accomplished in two steps, called Phase 1 and Phase 2, each of which requires changes to both the Galileo spacecraft software and to the supporting ground systems. This paper presents an overview of the Galileo mission and describes in some detail the changes required to implement both phases and which are under development by the worldwide Galileo team